Authenticating people, particularly remotely, has been a difficult operation to make resistant to attack. Since single authenticating techniques are vulnerable to theft, it has become attractive to various groups to devise ways to do multi factor authentication, where more than one of (something you have, something you know, something you are) is used in demonstrating the identity of a person whose identity is to be established.
Typically, doing this has involved using relatively complex or expensive devices such as cards with keyboards on them (where you authenticate to the card and then use it), fingerprint readers, or digital certificates requiring public/private encryption to validate the presenter is in possession both of a password and of a private key.
All this complexity has delayed widespread use of such systems, since the cost of giving out hundreds of millions of copies of them has been kept high by the need to authenticate two or more things, and the cost of building the system components.